You don't need much current or amps. I use a modded computer power supply at 12v it works fine. With the small of a current and amps I can stick my hands in find. Just make sure you don't have any open cuts. :)

You could get some 1/4-20 machine bolts with a counter sunk head. Drill and counter sink the holes the threw bolt the steel top too the wood. You could even drill the holes in the wood to say a 3/8 size and use a 1/4" fender washer to a allow for expansion and contraction.